1. Field of the Invention
Embodiments of the present invention generally relate to semiconductor processing, and more particularly, to apparatus for removing exhaust gases from semiconductor process chambers.
2. Description of the Related Art
Many films used in electronic device fabrication are formed in semiconductor process chambers using process gases that may be reacted to form a desired layer on the substrate. The process gases that do not react and gaseous byproducts formed during processing are then typically removed through an exhaust system of the process chamber.
Unfortunately, unreacted process gases and process gas byproducts can polymerize and/or condense on the surfaces of components of the exhaust system (e.g., within exhaust conduits). During continuous operation of the chamber, the polymerization and/or condensation of byproducts can result in the constant, gradual formation of highly viscous liquids or solids along the interior walls of the exhaust apparatus. As a result of this polymer build up, the exhaust apparatus can become at least partially blocked, reducing reactor exhaust flow efficiencies, increasing the possibility of substrate contamination, and generally reducing overall chamber performance.
To address this problem, some exhaust apparatus may include exhaust treatment devices such as heaters or RF power sources for treating the exhaust gases to prevent or reduce polymer formation within the exhaust apparatus. Unfortunately, these methods have drawbacks as well. For example, apparatus which utilize heaters to react excess gases from the process chamber have temperature constraints (such as, about 500 degrees Celsius), which cause byproducts to still remain. Moreover, while the exhaust gases may not condense or polymerize where heated, the polymerization may still occur downstream of the heater, once the exhaust gases start to cool. In addition, such systems do not work well for some processes. For example, such heating systems do not work well with reduced pressure deposition of polysilicon since polysilicon formation causes serious particle problems.
For reduced pressure polysilicon applications the exhaust gases may be treated with high frequency RF and nitrogen trifluoride (NF3) to chemically etch the exhaust deposit. However, this methodology may raise issues with fluorine contamination, materials compatibility, hazardous waste disposal, and serious damage to the exhaust apparatus if not used properly.
Thus, there is a need in the art for improved methods and apparatus for treating exhaust gases from semiconductor processes.